592 THE WONDER OF LIFE 



This capacity of registering experience and of utilizing 

 that registration in subsequent activities, appears to us 

 to be of the very essence of life. To take an instance that 

 seems simple, though it is probably very difficult, they say 

 that Venus's Fly Trap (Dioncea muscipula) when it has been 

 tricked several times in succession by stimuli which bring 

 it no satisfaction (or which do not lead on to the normal 

 sequences to which the plant has been habituated in Nature), 

 will cease to respond to the provocative stimuli. It passes 

 into a state of ' physiological sulks ' ; it becomes callous 

 to stimuli ; and this is the very best thing it could do, 

 short of catching hold of the tantalizing experimenter. 

 It almost remembers. 



It must be recognized that among the simpler animals, 

 such as Protozoa, Sponges, Zoophytes, Sea-Anemones, 

 Corals, Jellyfishes, Sea-Urchins, Starfishes, and simple 

 Worms, with not very much in the way of what are popu- 

 larly called ' habits ', there is great sensitiveness to stimulus 

 and a remarkable power of somehow registering experiences. 

 A starfish has no nerve-centres or ganglia at all ; that is to 

 say, the nerve cells of its nervous system are not concen- 

 trated, and indeed they have not sunk beneath the level 

 of the skin ; but the starfish has a remarkable power of 

 registering experiences and acting differently because it 

 does so. It has got far above the level of simply ' answering 

 back '. One reaches a higher level, of course, when there 

 is real and effective memory, for we cannot believe in more 

 than vague memory in creatures that have not nerve- 

 centres. For real and effective memory there must be 

 repositories or treasure-houses, such as nerve-centres 

 afford. 



(B) Individual Modifications. We see then that the 



